Focus detection device, focus adjustment device and camera

ABSTRACT

A focus detection device includes: a plurality of micro-lenses at which light fluxes through an image forming optical system enter, disposed in a two-dimensional array pattern; a plurality of light receiving elements disposed in correspondence to each of the plurality of micro-lenses; a focus detection unit that executes a detection of a defocus quantity of the image forming optical system by detecting, based upon outputs from the plurality of light receiving elements, a phase difference of a plurality of light fluxes through different areas of the image forming optical system; and a recognition unit that recognizes, based upon the outputs from the plurality of light receiving elements, characteristics of a subject image formed onto the plurality of light receiving elements via the plurality of micro-lenses, wherein: the focus detection unit detects the defocus quantity through a method optimal for the characteristics of the subject image recognized by the recognition unit.

TECHNICAL FIELD

The present invention relates to a focus detection device, a focusadjustment device and a camera.

BACKGROUND ART

Focus detection devices that detect focus through a method known as thephase difference detection method in the related art detect an extent ofimage subject image shift based upon the outputs from a plurality oflight receiving elements arrayed in correspondence to each ofmicro-lenses disposed in a two-dimensional pattern. Patent literature 1,for instance, describes a focus detection device that detects contrastalong a plurality of directions and selects an optimal focus detectiondirection among the plurality of directions based upon the detectedcontrast.

CITATION LIST Patent Literature

Patent literature 1: Japanese Laid Open Patent Publication No.2009-198771

SUMMARY OF INVENTION Technical Problem

There is an issue with the related art in that accurate and efficientfocus adjustment cannot always be assured, i.e., focus adjustment forcertain types of subjects may be less than accurate or efficient.

Solution to Problem

According to the 1st aspect of the present invention, a focus detectiondevice comprises: a plurality of micro-lenses at which light fluxeshaving been transmitted through an image forming optical system enter,disposed in a two-dimensional array pattern; a plurality of lightreceiving elements disposed in correspondence to each of the pluralityof micro-lenses; a focus detection unit that executes a detection of adefocus quantity of the image fowling optical system by detecting, basedupon outputs from the plurality of light receiving elements, a phasedifference manifested by a plurality of light fluxes having passedthrough different areas of the image forming optical system; and arecognition unit that recognizes, based upon the outputs from theplurality of light receiving elements, characteristics of a subjectimage formed onto the plurality of light receiving elements via theplurality of micro-lenses, wherein: the focus detection unit detects thedefocus quantity through a method optimal for the characteristics of thesubject image recognized by the recognition unit.

According to the 2nd aspect of the present invention, in the focusdetection device according to the 1st aspect, the characteristics of thesubject image may manifest as a pattern in the subject image.

According to the 3rd aspect of the present invention; a focus adjustmentdevice comprises: a plurality of micro-lenses disposed in atwo-dimensional array pattern so as to allow light fluxes, having beentransmitted through an image forming optical system, to enter thereat; aplurality of light receiving elements disposed in correspondence to eachof the plurality of micro-lenses on a rear side of the micro-lens; arecognition unit that recognizes, based upon light reception outputsfrom the plurality of light receiving elements, a pattern in a subjectimage formed onto the plurality of light receiving elements via theplurality of micro-lenses; and a focus adjustment unit that executesfocus adjustment for the image forming optical system by detecting,based upon the light reception outputs, a phase difference manifested bya pair of light fluxes having passed through different areas of theimage forming optical system, wherein: the focus adjustment unitexecutes focus adjustment optimal for the pattern in the subject imagerecognized by the recognition unit.

According to the 4th aspect of the present invention, in the focusadjustment device according to the 3rd aspect, the recognition unit maybe capable of recognizing at least a cyclical pattern, an edge patternand a gradation pattern.

According to the 5th aspect of the present invention, it is preferredthat in the focus adjustment device according to the 3rd or 4th aspect,in correspondence to the pattern in the subject image recognized by therecognition unit, the focus adjustment unit switches at least one of;positions of a plurality of light receiving elements selected forpurposes of generating a pair of signal strings for phase differencedetection, a width represented by the pair of signal strings, a quantityof light receiving elements to be used when generating the pair ofsignal strings and whether or not to remove a low-frequency signal fromthe pair of signal strings.

According to the 6th aspect of the present invention, in the focusadjustment device according to any one of the 3rd through 5th aspects,the focus adjustment unit may make a decision, based upon the pattern inthe subject image recognized by the recognition unit, as to whether ornot the detected phase difference indicates a false focus match.

According to the 7th aspect of the present invention, in the focusadjustment device according to the 6th aspect upon deciding that thedetected phase difference indicates the false focus match, the focusadjustment unit may again detect the phase difference based upon thepair of light fluxes forming a smaller opening angle.

According to the 8th aspect of the present invention, in the focusadjustment device according to the 6th aspect upon deciding that thedetected phase difference indicates the false focus match, the focusadjustment unit may reverse a direction along which a focusing lensincluded in the image forming optical system is driven.

According to the 9th aspect of the present invention, in the focusadjustment device according to any one of the 6th through the 8thaspects if the recognition unit recognizes a nonuniform pattern formed,via each of the plurality of micro-lenses, on the plurality of lightreceiving elements disposed on the rear side of the micro-lens, and thedetected phase difference is equal to or less than a predeterminedthreshold value, the focus adjustment unit may decide that the detectedphase difference indicates the false focus match.

According to the 10th aspect of the present invention, a focusadjustment device comprises: a plurality of micro-lenses disposed in atwo-dimensional array pattern so as to allow light fluxes, having beentransmitted through an image forming optical system that includes afocusing lens, to enter thereat; a plurality of light receiving elementsdisposed in correspondence to each of the plurality of micro-lenses atpositions at which the light fluxes, having been transmitted through themicro-lens, enter; a recognition unit that recognizes, based upon lightreception outputs from the plurality of light receiving elements, acyclical pattern in a subject image formed via the plurality ofmicro-lenses on the plurality of light receiving elements; a phasedifference detection unit that detects, based upon the light receptionoutputs, a phase difference manifested by a pair of light fluxes havingpassed through different areas of the image forming optical system; andthe focus adjustment unit that executes focus adjustment for the imageforming optical system by driving the focusing lens based upon the phasedifference detected by the phase difference detection unit, wherein: ifthe cyclical pattern is recognized by the recognition unit, the focusadjustment unit drives the focusing lens along a direction in whichcycles in the cyclical pattern are lengthened.

According to the 11th aspect of the present invention, in the focusadjustment device according to the 10th aspect the recognition unit mayexecute a Fourier transform on the light reception outputs andrecognizes the cyclical pattern in a spatial frequency range.

According to the 12th aspect of the present invention, in the focusadjustment device according to the 10th or 11th aspect the recognitionunit may recognize the cyclical pattern by detecting edges from lightreception outputs from the plurality of light receiving elementscorresponding to at least one micro-lens among the plurality ofmicro-lenses.

According to the 13th aspect of the present invention, in the focusdetection device according to the 10th or 11th aspect the recognitionunit may recognize the cyclical pattern by calculating sums of lightreception outputs from the plurality of light receiving elementscorresponding to at least two micro-lenses among the plurality ofmicro-lenses and comparing the two sums.

According to the 14th aspect of the present invention, a camera equippedwith the focus adjustment device according to any one of the 3rd through13th aspects.

Advantageous Effect of the Invention

The present invention enables accurate and efficient focus adjustment incorrespondence to a subject pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

(FIG. 1) A sectional view of a camera system, used in conjunction withinterchangeable lenses, which may adopt the present invention

(FIG. 2) Perspective of the focus detection unit 104

(FIG. 3) A schematic illustration of the ranges over which light fluxesfrom the micro-lenses 13 enter, superimposed over the light-receivingsurface of the light receiving element array 12

(FIG. 4) An illustration of the focus detection method adopted by thebody control device 101

(FIG. 5) A schematic illustration showing a condition in which focusmatch is achieved for the focus adjustment target subject

(FIG. 6) A schematic illustration showing a condition in which focusmatch is not achieved for the focus adjustment target subject

(FIG. 7) Examples of patterns that may be recognized by the body controldevice 101

(FIG. 8) A flowchart of focus adjustment control executed by the bodycontrol device 101

(FIG. 9) A flowchart of the light reception pattern recognitionprocessing called up in step S130 in FIG. 8

(FIG. 10) An example of a cyclical pattern that may be recognized by thebody control device 101

(FIG. 11) A flowchart of focus adjustment control executed by the bodycontrol device 101

(FIG. 12) A flowchart of the false focus match detection processingcalled up in step S350 in FIG. 11

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 1 is a sectional view of a camera system, used in conjunction withinterchangeable lenses, which adopts the present invention. A camera 1comprises a camera body 100 and an interchangeable lens 200 that can bemounted at/dismounted from the camera body 100.

At the interchangeable lens 200, a photographic optical systemcomprising a plurality of lenses 202, 203 and 204, and an aperture 205having an opening portion are disposed. A light flux departing a subjectpasses through the photographic optical system and the opening portionof the aperture 205 before entering the camera body 100. It is to benoted that while FIG. 1 shows the photographic optical system made upwith three lenses, the photographic optical system may include anynumber of lenses. In addition, while the aperture 205 in FIG. 1 isdisposed between the lens 203 and the lens 204, the aperture 205 mayinstead be disposed further frontward or rearward relative to thephotographic optical system or between other lenses, as known in therelated art.

The lens 203 included in the photographic optical system is a focusinglens used to adjust the focusing position for the photographic opticalsystem. The focusing lens 203 is connected to a lens drive device 206via a drive mechanism (not shown) configured with gears and the like.The lens drive device 206, which includes an actuator (not shown) suchas a stepping motor, drives the focusing lens 203 in direction D runningalong an optical axis L of the photographic optical system.

An aperture drive device 207 is connected to the aperture 205. Theaperture drive device 207, which includes an actuator (not shown) suchas a stepping motor, alters the opening radius R at the aperture 205 bydriving a drive mechanism (not shown).

An image sensor 102 such as a CCD sensor or a CMOS sensor, capable ofcapturing a subject image formed by the photographic optical system, isdisposed at the camera body 100. The image sensor 102 is disposed sothat its imaging plane matches a pre-determined focal plane of thephotographic optical system. A half mirror 103 is disposed between thephotographic optical system and the imaging plane of the image sensor102 within the camera body 100. The half mirror 103, which may beconfigured with, for instance, a pellicle mirror, allows part of thesubject light having departed the photographic optical system to betransmitted toward the image sensor 102 and reflects the remainingsubject light toward the top of the camera body 100. The reflected lightenters a focus detection unit 104 disposed on the upper side in thecamera body 100. Structural features of the focus detection unit 104will be described in detail later.

A body control device 101 comprising a microprocessor and its peripheralcircuits is disposed at the camera body 100. The body control device 101controls various units at the camera body 100 by executing a specificcontrol program read out from a storage medium (not shown) where theprogram is stored in advance. The interchangeable lens 200 includes alens control device 201 likewise comprising a microprocessor and itsperipheral circuits. The lens control device 201 controls various unitsin the interchangeable lens 200 by executing a specific control programread out from a storage medium (not shown) where the control program isstored in advance. It is to be noted that the body control device 101and the lens control device 201 may each be configured with anelectronic circuit capable of executing operation equivalent to thecontrol program.

The body control device 101 and the lens control device 201 areconfigured so as to be able to communicate with each other via anelectric contact point (not shown) disposed in the vicinity of the lensmount. Through data communication enabled via the electric contactpoint, the body control device 101 transmits, for instance, a drivecommand for the focusing lens 203 and a drive command for the aperture205 to the lens control device 201. It is to be noted that the datacommunication may be carried out through a method (e.g., wirelesscommunication or optical communication) other than the electrical signalexchange via the electric contact point.

In response to a specific focus adjustment operation (e.g., a halfwaypress operation of a shutter release switch (not shown)) the bodycontrol device 101 detects a defocus quantity representing the extent ofdefocus based upon an output from the focus detection unit 104 andtransmits a drive command to the lens control device 201 so as to drivethe focusing lens 203 by an extent corresponding to the defocusquantity. In response to this drive command, the lens control device 201engages the lens drive device 206 to drive the focusing lens 203.Consequently, a focus match is achieved for a specific subject.

A monitor 110 constituted with, for instance, a liquid crystal displayelement, is disposed on the rear surface of the camera 1. The bodycontrol device 101 uses this monitor 110 when, for instance, reproducingstill image data or movie image data obtained through a shootingoperation, displaying a settings menu in which photographing parameters(aperture number, shutter speed and the like) can be selected for thecamera 1, displaying a live view image and the like.

An electronic viewfinder unit 108, which includes a display element suchas a liquid crystal display element, is disposed at an upper portion ofthe camera body 1. The photographer is able to view a subject image orthe like displayed at the display element of the electronic viewfinderunit 108 via an eyepiece lens 106 through a finder portion 107. When thecamera 1 is set in the photographing mode, the body control device 101engages the image sensor 102 so as to capture a subject image overpredetermined intervals (e.g., every 1/60 sec), generates a live viewimage based upon the image capturing signals and displays the live viewimage thus created at the monitor 110 or the electronic viewfinder unit108.

In response to a specific still image shooting operation (e.g., a fullpress operation of the shutter release switch (not shown)) performed inthe photographing mode, the body control device 101 executesphotographing control. At this time, the body control device 101 engagesthe image sensor 102 to capture the subject image by controlling theshutter and the like (not shown). It then executes various types ofimage processing on image capturing signals output from the image sensor102 and stores still image data generated through the image processinginto a storage medium (not shown) such as a memory card.

(Description of the Focus Detection Unit 104)

FIG. 2 shows the focus detection unit 104 in a perspective. The focusdetection unit 104 comprises a micro-lens array 11 and a light receivingelement array 12 disposed further rearward relative to the micro-lensarray 11.

Numerous micro-lenses 13 are disposed in a two-dimensional pattern atthe micro-lens array 11. Subject light having been reflected at the halfmirror 103 passes through a micro-lens 13 among the micro-lenses 13 andenters the light-receiving surface of the light receiving element array12. Numerous light receiving element groups 14 where light fluxes havingpassed through individual micro-lenses 13 enter are arrayed in atwo-dimensional pattern at the light-receiving surface (the surfacefacing toward the micro-lens array 11) of the light receiving elementarray 12. Each light receiving element group is made up with 25 lightreceiving elements disposed in a 5 (row)×5 (column) array. A light fluxhaving passed through a given micro-lens 13 enters one of the lightreceiving element groups 14, and the plurality of light receivingelements constituting the particular light receiving element group 14receives the light flux.

The area of the surface of the micro-lens array 11 (the surface wherethe subject light enters) over which no micro-lens 13 is present isshielded with a light-blocking mask. For this reason, only a light fluxthat has passed through a micro-lens 13 is allowed to enter the lightreceiving element array 12.

The light receiving element array 12 is disposed at a position set apartfrom the micro-lens array 11 by a distance equal to the focal length ofthe micro-lenses 13. In order to assure clarity in the illustration, thedistance “d” between the micro-lens array 11 and the light receivingelement array 12 is exaggerated in FIG. 2.

It is to be noted that FIG. 2 only shows part of the micro-lens array 11and part of the light receiving element array 12. Namely, the actualmicro-lens array and light receiving element array include greaternumbers of micro-lenses 13 and light receiving element groups 14. Inaddition, the quantity of light receiving elements included in eachlight receiving element group 14 may be more than or fewer than 25 andthe light receiving elements may be arrayed in a pattern other than thatshown in FIG. 2.

FIG. 3 is a schematic illustration of the ranges of entry of lightfluxes, having departed micro-lenses 13, superimposed over thelight-receiving surface of the light receiving element array 12. Whenthe f-number of the photographic optical system matches the f-number ofthe micro-lenses 13, a light flux having departed a given micro-lens 13enters within the range of a circle 15 enclosing a light receivingelement group 14. When the aperture 205 is constricted and the f-numberat the photographic optical system takes on a value greater than thef-number of the micro-lenses 13 (when the photographic optical system isdarkened relative to the micro-lenses 13), the size of the circles 15becomes smaller than that shown in FIG. 3.

It is to be noted that when the f-number at the photographic opticalsystem is set to a value smaller than the f-number of the micro-lenses13 (i.e., when the photographic optical system is rendered lighterrelative to the micro-lenses 13), the size of the circles 15 becomesgreater than that shown in FIG. 3 and individual circles 15 overlap oneanother. Namely, crosstalk between light fluxes having passed throughthe micro-lenses 13 occurs. If light fluxes having passed through aplurality of micro-lenses 13 enter a single light receiving element inthis state, accurate focus detection is no longer possible. During focusdetection, the body control device 101 in the embodiment adjusts theaperture 205 so as to match the f-number at the photographic opticalsystem with the f-number of the micro-lenses 13. In other words, thecrosstalk phenomenon described above does not occur during focusdetection since it is ensured that each subject light flux enters withinthe range of a circle 15 shown in FIG. 3.

(Description of the Focus Detection Method)

The body control device 101 detects the focal point through the methodknown as the phase difference detection method whereby an image shiftquantity, i.e., the extent of image shift pertaining to the subjectimage, is detected based upon an output from the focus detection unit104. The following is a description of the focus detection methodadopted by the body control device 101.

FIG. 4( a) shows a single row of light receiving element groups 14engaged in focus detection among the numerous light receiving elementgroups 14 shown in FIG. 3. While FIG. 4( a) shows only 5 light receivingelement groups 14, it is desirable to select a greater number of lightreceiving element groups 14 for focus detection. In the followingdescription, different reference numerals 14 a through 14 e are used torefer to the individual light receiving element groups 14.

FIG. 4( b) is a schematic illustration of the relationships between thelight receiving element groups 14 a through 14 e and the focus detectionpupils. The micro-lenses 13 a through 13 e are disposed so that theirapexes are substantially in alignment with a predetermined focal plane17 of the photographic optical system. The micro-lens 13 c projects theshapes of a pair of light receiving elements 16 lc and 16 rc disposed tothe rear thereof onto an exit pupil 20 set apart from the micro-lens 13c by a projecting distance d2, and the shapes of the light receivingelements thus projected form focus detection pupils 21 and 22. Theprojecting distance d2 is determined in correspondence to the curvatureand the refractive index of the micro-lens 13 c, the distance betweenthe micro-lens 13 c and the light receiving element array 12, and thelike. The pair of focus detection pupils 21 and 22 and the pair of lightreceiving elements 161 c and 16 rc achieve a relationship conjugate witheach other via the micro-lens 13 c.

It is to be noted that while an explanation has been given above inreference to the pair of light receiving elements 16 lc and 16 rcbelonging to the light receiving element group 14 c set on the opticalaxis L and the pair of focus detection pupils 21 and 22 so as tosimplify the description, a pair of light receiving elements in a lightreceiving element group taking up a position away from the optical axisL, too, receive a light flux arriving at the corresponding micro-lensfrom a pair of focus detection pupils.

The light receiving element 16 lc outputs a light reception signalcorresponding to the intensity of an image formed on the micro-lens 13 cwith a focus detection light flux 24 having passed through the focusdetection pupil 22 and traveled toward the micro-lens 13 c. Likewise,the light receiving element 16 rc outputs a light reception signalcorresponding to the intensity of an image formed on the micro-lens 13 cwith a focus detection light flux 23 having passed through the focusdetection pupil 21 and traveled toward the micro-lens 13 c.

Accordingly, information pertaining to intensity distributions of a pairof images formed on the light receiving element array 12 with focusdetection light fluxes each passing through the focus detection pupil 21and 22 can be obtained by acquiring the light reception outputs of eachpair of light receiving elements corresponding to the focus detectionpupil 21 and the focus detection pupil 22 from the plurality of lightreceiving element groups 14 a through 14 e disposed along a straightline, as shown in FIG. 4( a). By executing an image shift detectionoperation of the known art in conjunction with the information thusacquired, an image shift quantity representing the extent of image shiftmanifested by the pair of images is detected through a detection methodcommonly referred to as the split pupil phase difference detectionmethod. Then, the image shift quantity is converted in correspondence tothe distance between the gravitational centers of the pair of focusdetection pupils 21 and 22 so as to calculate a defocus quantityrepresenting the deviation of the current imaging plane relative to thepredetermined focal plane.

The image shift detection operation and the conversion operation will bedescribed in more specific terms. The body control device 101 firstdesignates the value obtained by adding together the light receptionoutputs of the three middle light receiving elements 16 la at the leftend column in the light receiving element group 14 a as a(1). Likewise,it calculates the sums a(2) through a(5) in correspondence to the lightreceiving element groups 14 b through 14 e, each by adding together thelight reception outputs of the three middle light receiving elements 16lb, 16 lc, 16 ld or 16 le at the left end column in the correspondinglight receiving element group. Next, for the light receiving elementgroups 14 a through 14 e, it calculates sums by adding together thelight reception outputs of the three middle light receiving elements 16ra through 16 re at the right end columns and designates the sums asb(1) through b(5). A pair of signal strings a(i) and b(i) generated asdescribed above constitutes information pertaining to the intensitydistribution of the pair of images mentioned earlier. The body controldevice 101 executes a correlation operation for the pair of signalstrings by individually offsetting the signal strings in small steps andcalculates a correlation quantity in correspondence to each offsetquantity. Then, based upon the correlation quantity calculation results,it determines the offset quantity in correspondence to which a minimumcorrelation quantity is calculated (the offset quantity at which amaximum degree of correlation quantity manifests). The body controldevice 101 multiplies the offset quantity by a predetermined conversioncoefficient in order to calculate a defocus quantity representing theextent of defocusing manifested by the subject image relative to thepredetermined focal plane.

It is to be noted that the row of light receiving element groups 14 tobe engaged in focus detection, among the numerous light receivingelement groups 14, may be selected through any method. For instance, theuser may be asked to specify the position of the focusing target subjectand light receiving element groups 14 present at the particular positionmay be selected. As an alternative, light receiving element groups 14present at a predetermined position, such as the center of thephotographic field, may be selected.

(Description of a Cyclical Pattern Formed on the Light-ReceivingSurface)

For each session of focus detection and focus adjustment, the bodycontrol device 101 recognizes, through a pattern-matching technology ofthe known art, the pattern of an image formed via the micro-lenses 13onto the light-receiving surface of the light receiving element array12. Based upon the recognized pattern, it alters the specific details ofthe focus detection and the focus adjustment. The following is adescription of the pattern of an image formed on the light-receivingsurface of the light receiving element array 12.

FIG. 5 is a schematic illustration of a subject 31, a photographingoptical system 30, a subject image 33, the predetermined focal plane 17,the micro-lens array 11 and the light receiving element array 12 in astate in which the focus adjustment target subject is in focus. It is tobe noted that the photographic optical system is represented by a singlelens in the schematic illustration in FIG. 5.

When a focus match is achieved for the focus adjustment target subject31, the image (subject image) 33 of the subject 31, formed by thephotographic optical system 30, is substantially in alignment with thepredetermined focal plane 17, and a light flux 35, having departed apoint 32 on the subject 31 and passed through the photographic opticalsystem 30, has converged so that its section is smaller than thepermissible circle of confusion on the predetermined focal plane 17, asillustrated in FIG. 5( a).

FIG. 5( b) shows an area near the focus detection unit 104 in anenlarged view. In this condition, a light flux having departed a point34 on the subject image 33 enters with substantial uniformity on therear side of the micro-lens 13 c, as illustrated in FIG. 5( c). Thelight flux, having departed the point 34, does not enter any of theother micro-lenses 13, and no light flux from any other point on thesubject image 33 enters on the rear side of the micro-lens 13 c.

FIG. 6 is a schematic illustration of the subject 31, the photographicoptical system 30, the subject image 33, the predetermined focal plane17, the micro-lens array 11 and the light receiving element array 12 ina state in which the focus adjustment target subject is not in focus.

When the image 33 of the subject 31, formed via the photographic opticalsystem 30, is set apart from the predetermined focal plane 17 by adistance equal to or greater than twice the focal length of themicro-lenses 30, the light flux 35, having departed the point 32 on thesubject 31 and passed through the photographic optical system 30 reachesthe predetermined focal plane 17 as light widening over a certain range,as illustrated in FIG. 6( a). This means that the light flux 35, havingdeparted the point 32, enters a plurality of micro-lenses 13. Inaddition, as illustrated in the enlarged view in FIG. 6( b), lightfluxes, having departed a plurality of points on the subject image 33,enter a single micro-lens 13 c. As a result, an image 36 is projectedonto the rear side of the micro-lens 13 c in correspondence to the shapeof the subject image 33 and the positional relationship between thesubject image 33 and the micro-lenses 13.

Next, patterns that may be recognized by the body control device 101 tobe used for focus detection and focus adjustment in the embodiment willbe described in reference to the examples presented in FIG. 7.

FIG. 7( a 1) shows a subject image 33 a with vertical stripes. If thissubject image 33 a is formed at a position somewhat set apart from thepredetermined focal plane 17, the pattern shown in FIG. 7( a 2) isformed on the light-receiving surface of the light receiving elementarray 12. In this situation, the light reception outputs obtained fromlight receiving elements set consecutively along the lateral directionin a single row in a given light receiving element group 14 will includea plurality of peaks each in correspondence to a vertical stripe.

The body control device 101 determines that the subject 31 is a cyclicsubject taking on a cyclical pattern in a case such as this in which thelight reception outputs of the light receiving elements set side-by-sidein a single row along a specific direction within a given lightreceiving element group 14 include a plurality of peaks. In thissituation, if the absolute value of the defocus quantity is less than apredetermined threshold value (i.e., if the current condition is judgedto be a focus match state) in the subsequent focus detection operation,the particular defocus quantity is determined to be incorrect (i.e., thecurrent condition is a false focus match state). The rationale for thisdecision-making is that if a focus match was achieved for the subject31, a uniform light flux would enter at a single light receiving elementgroup 14 as illustrated in FIG. 5( c) and that a pattern such as thatshown in FIG. 7( a 2) could never be formed in a true focus match state.

Upon determining that the defocus quantity is incorrect (i.e., thecurrent condition is a false focus match state), the body control device101 re-executes the focus detection operation by reducing the angle ofdetection range. Namely, instead of the light receiving elements at thetwo end columns on the left side and the right side shown in FIG. 4( a),light receiving elements at inner positions are used to create a pair ofsignal strings and the image shift detection operation and theconversion operation are executed in conjunction with the pair of signalstrings thus created.

The subject image shown in FIG. 7( b 1) will be explained next. FIG. 7(b 1) shows a subject image 33 b with a clear boundary (edge) dividing italong the left/right direction. If this subject image 33 b is formed ata position somewhat set apart from the predetermined focal plane 17, thepattern shown in FIG. 7( b 2) is formed on the light-receiving surfaceof the light receiving element array 12.

If outputs completely different from each other (e.g., circles 15 a and15 c) are detected from a pair of light receiving element groups 14present in close proximity to each other and these two different outputsare inverted in the output from a light receiving group 14 (e.g., acircle 15 b) present between the pair of light receiving element groups,the body control device 101 determines that the subject 31 is an edgesubject assuming an edge pattern. In the subsequent focus detectionoperation, it generates a pair of signal strings to be used in imageshift detection operation from light receiving element groups 14 setside-by-side in a single row running perpendicular to the detected edge.In addition, the light receiving element groups 14, the outputs fromwhich are to be sampled in order to generate the pair of signal strings,are selected from a range narrower than normal and thus, the signalstrings assume a length smaller than normal. The rationale for this isthat since there is obviously a well-defined edge, only an area aroundthe edge needs to be the focus detection target.

The subject image shown in FIG. 7( c 1) will be explained next. FIG. 7(c 1) shows a subject image 33 c with a gradation pattern manifesting agradual change in luminance or chromaticity along the up/down direction.If this subject image 33 c is formed at a position somewhat set apartfrom the predetermined focal plane 17, the pattern shown in FIG. 7( c 2)is formed on the light-receiving surface of the light receiving elementarray 12.

If a plurality of light receiving element groups 14 disposed in closeproximity to one another output light reception data uniformlyindicating a gradual change (or indicating hardly any change), the bodycontrol device 101 determines that the subject 31 is a gradation subjectwith a gradation pattern. Subsequently, after generating a pair ofsignal strings, it directly executes an image shift detection operationwithout applying a high pass filter processing, which would normally beexecuted on the signal strings in order to remove an excesslow-frequency component. In addition, if the difference between the highsignal level and the low signal level in the pair of signal stringshaving been generated is less than a predetermined value, it determinesthat the subject 31 is a low contrast subject, requiring improvedaccuracy in the image shift detection operation and, accordingly, itgenerates a pair of signal strings by sampling data from a greaternumber of light receiving elements. For instance, it may generate a pairof signal strings by calculating the sum of the outputs from six lightreceiving elements instead of the sum of outputs from three lightreceiving elements as shown in FIG. 4( a).

As described above, the body control device 101 in the embodimentcustomizes the details of the focus detection operation so as to executefocus detection operation best suited for the specific pattern of theimage formed via the micro-lenses 13 onto the light receiving elementarray 12. As explained earlier, the body control device 101 recognizesthree different patterns (a cyclical pattern, an edge pattern and agradation pattern) such as those shown in FIG. 7( a 1) through FIG. 7( c1) through a pattern matching operation of the known art. There are norestrictions imposed with regard to the mariner with which the patternmatching operation is executed, as long as at least these three patternscan be recognized through the operation.

(Description of Focus Adjustment Control)

FIG. 8 presents a flowchart of focus adjustment control executed by thebody control device 101. The processing shown in FIG. 8 is included in acontrol program read out from a memory (not shown) and executed by thebody control device 101.

First, in step S100, the body control device 101 makes a decision as towhether or not the user has performed a specific focus adjustmentoperation (e.g., halfway press operation at the shutter release switch).Until the user performs a focus adjustment operation, the body controldevice 101 repeatedly executes step S100 and once a focus adjustmentoperation is executed, the operation proceeds to step S110. In stepS110, the body control device 101 executes charge control of the lightreceiving element array 12 and then, in step S120, it reads out thelight reception outputs from the individual light receiving elementgroups 14. In step S130, the body control device 101 executes lightperception pattern recognition processing (to be described later) basedupon the light reception outputs having been read out and recognize apattern that may be one of those shown in FIG. 7( a 1) through FIG. 7( c1).

In step S140, the body control device 101 executes an image shiftdetection operation and a conversion operation by reflecting the lightreception pattern recognition results in the details thereof inconjunction with part of the light reception outputs having been readout in step S120, and calculates a defocus quantity through theseoperations. In step S150, it calculates a drive quantity representingthe extent to which the focusing lens 203 needs to be driven to achievea focus match based upon the defocus quantity. In step S160, a decisionis made as to whether or not the focusing lens 203 needs to be driven,i.e., whether or not a focus match state has already been achieved, andif the current condition is already a focus match state, the processingin FIG. 8 ends. If a focus match state has not been achieved, theoperation proceeds to step S170, in which the body control device 101executes lens drive control before the operation returns to step 110.The body controls device 101 executing the lens drive control transmitsa drive instruction to the lens control device 201 so that the focusinglens 203 is driven by an extent corresponding to the lens drive quantityhaving been calculated in step S150. In response to this driveinstruction, the lens control device 203 engages the lens drive device206 in operation to drive the focusing lens 203.

FIG. 9 presents a flowchart of the light reception pattern recognitionprocessing called up in step S130 in FIG. 8. As is the processing shownin FIG. 8, this processing is included in the control program executedby the body control device 101. First, in step S200, the body controldevice 101 extracts a characteristic quantity pertaining to the imageprojected via the micro-lenses 13 based upon the light reception outputsfrom the individual light receiving element groups 14. Thecharacteristic quantity is determined in correspondence to a color, ashape, a height, a position, a width, an area and the like pertaining tothe image, and no restrictions whatsoever are imposed with regard to thecharacteristic quantity as long as it enables recognition of at leastthree different types of patterns such as those shown in FIG. 7( a 1)through FIG. 7( c 1). In the following step S210, the body controldevice 101 recognizes a pattern based upon the extracted characteristicquantity

In step S220, the body control device 101 makes a decision as to whetheror not the recognized pattern is a cyclical pattern. Upon deciding thata cyclical pattern has been recognized, the operation proceeds to stepS270 to select the focus detection/focus adjustment setting for acyclical subject. Namely, a setting whereby a defocus quantity, theabsolute value of which is less than a predetermined threshold value(i.e., indicating a focus match state) is determined to be incorrect(i.e., the current condition is a false focus match state) is selected.Upon deciding that the defocus quantity is incorrect (the currentcondition is a false focus match state), the body control device 101re-executes the focus detection calculation by narrowing the angle ofdetection range.

If a cyclical pattern has not been recognized, the operation proceeds tostep S230 to make a decision as to whether or not the recognized patternis an edge pattern. If an edge pattern has been recognized, theoperation proceeds to step S260, in which the focus detection/focusadjustment setting for an edge subject is selected. Namely, a pair ofsignal strings to be used for purposes of image shift detectionoperation is generated by sampling data output from light receivingelement groups 14 set in a single row running perpendicular to thedirection in which the detected edge runs. In addition, the lightreceiving element groups 14, the outputs from which are to be sampled inorder to generate the pair of signal strings, are selected from anarrower range than normal, so as to reduce the length of the signalstrings relative to the regular signal string length.

If an edge pattern has not been recognized, the operation proceeds tostep S240 to make a decision as to whether or not the recognized patternis a gradation pattern. If a gradation pattern has been recognized, theoperation proceeds to step S250, in which the focus detection/focusadjustment setting for a gradation subject is selected. Namely, once apair of signal strings has been generated, an image shift detectionoperation is executed without applying a high pass filter to the signalstrings. In addition, if the difference between the high signal leveland the low signal level in the pair of signal strings having beengenerated is less than a predetermined value, the subject 31 is judgedto be a low contrast subject requiring improved accuracy in the imageshift detection operation, and accordingly, a pair of signal strings isgenerated by sampling data from a greater number of light receivingelements.

The camera system in the first embodiment described above achieves thefollowing advantages.

(1) Based upon the light reception outputs from light receiving elementgroups 14, each disposed on the rear side of one of a plurality ofmicro-lenses 13 disposed in a two-dimensional array and each made upwith a plurality of light receiving elements, the body control device101 recognizes the pattern of a subject image formed via the pluralityof micro-lenses 13 onto the light-receiving surface of the lightreceiving element array 12, and executes focus adjustment optimal forthe recognized pattern by detecting the phase difference between a pairof light fluxes having passed through different areas of thephotographic optical system based upon light reception outputs providedfrom the light receiving element array 12. As a result, accurate andefficient focus adjustment optimal for the subject pattern is enabled.

(2) After recognizing a cyclical pattern, the body control device 101determines that the current condition is a false focus match state, evenif a focus match state is detected, and re-executes the focus detectionoperation by narrowing the angle of detection range. Through thesemeasures, accurate and efficient focus adjustment is enabled even whenthe subject has, for instance, a striped pattern, which tends to readilycause a false focus match.

(3) Upon recognizing an edge pattern, the body control device 101selects fewer than usual light receiving element groups 14 from lightreceiving element groups 14 set consecutively in a single row runningperpendicular to the detected edge, and generates a pair of signalstrings to be used for purposes of image shift detection operation, bysampling outputs from the selected light receiving element groups 14.Through these measures, accurate and efficient focus adjustment isachieved for a subject with a clearly defined edge by excluding anyinfluence of noise and the like present in areas other than the edgearea. In addition, since signal strings that are shorter than normal areused, the focus detection operation can be executed at higher speed.

(4) Upon recognizing a gradation pattern, the body control device 101generates a pair of signal strings and then immediately executes animage shift detection operation without applying a high pass filter tothe signal strings. In addition, if the difference between the highsignal level and the low signal level in the pair of signal stringshaving been generated is less than a predetermined value, it decidesthat the subject 31 is a low contrast subject requiring improvedaccuracy in the image shift detection operation and accordingly,generates a pair of signal strings by sampling outputs from a greaternumber of light receiving elements. Through these measures, accurate andefficient focus adjustment is achieved for a subject such as a gradationsubject for which focus detection cannot be easily executed.

Second Embodiment

The camera system in this embodiment adopts a structure identical tothat of the camera system achieved in the first embodiment shown inFIG. 1. The second embodiment only differs from the first embodiment inthe focus detection processing executed by the body control device 101.The following explanation will focus on the feature of the currentembodiment distinguishing it from the first embodiment, and a repeatedexplanation of other aspects of the embodiment similar to those of thefirst embodiment will not be provided.

FIG. 10( a) shows a subject image 43 a with vertical stripes runningalong the up-down direction. The vertical stripes in the subject image43 a are set over cycles T1 along the lateral direction, therebyachieving a cyclical pattern. When the subject image 43 a is formed at aposition somewhat set apart from the predetermined focal plane 17, thecyclical pattern shown in FIG. 10( b) is formed onto the light-receivingsurface of the light receiving element array 12. By executing thepattern matching processing explained earlier on the light receptionoutputs from the light receiving element array 12, the body controldevice 101 recognizes the cyclical pattern such as that shown in FIG.10( a) of the subject 31. The body control device 101, having recognizedsuch a cyclical pattern, decides in the subsequent focus detectionoperation that any defocus quantity, the absolute value of which is lessthan a predetermined threshold value (i.e., indicating a focus matchstate), is incorrect (i.e., the current condition is a false focus matchstate).

Upon deciding that the defocus quantity is incorrect (i.e., the currentcondition is a false focus much state), the body control device 101engages the lens drive device 203 in operation so as to drive thefocusing lens 203 by a specific extent along the direction in which thecycles of the cyclical pattern having been recognized are lengthened andthen re-executes the focus detection operation. For instance, if thecurrent false focus match state results from focus adjustment havingbeen executed by driving the focusing lens 203 along the directiontoward infinity, it will drive the focusing lens 203 along the oppositedirection (toward close-up). Through these measures, the cyclicalpattern with the cycles T2 shown in FIG. 10( b) is altered to a cyclicalpattern shown in FIG. 10( c) with cycles T3, longer than the cycles T2.

(Description of Focus Adjustment Control)

FIG. 11 presents a flowchart of the focus adjustment control executed bythe body control device 101. The processing shown in FIG. 11 is includedin a control program read out from a memory (not shown) and executed bythe body control device 101.

First, in step S300, the body control device 101 makes a decision as towhether or not the user has performed a specific focus adjustmentoperation (e.g., a halfway press operation at the shutter releaseswitch). Until the user performs a focus adjustment operation, the bodycontrol device 101 repeatedly executes step S300 and once a focusadjustment operation is executed, the operation proceeds to step S310.In step S310, the body control device 101 executes charge control of thelight receiving element array 12 and then, in step S320, it reads outthe light reception outputs from the individual light receiving elementgroups 14.

In step S330, the body control device 101 executes an image shift (phasedifference) detection operation and a conversion operation inconjunction with part of the light reception outputs having been readout in step S320 and calculates a defocus quantity through theseoperations. Then, in step S360, a decision is made as to whether or notthe focusing lens 203 needs to be driven, i.e., whether or not thecurrent condition is already a focus match state, and if it is decidedthat a focus match state has already been achieved, the operationproceeds to step S350. If, on the other hand, it is decided that a focusmatch state has not been achieved, the operation proceeds to step S370to calculate a drive quantity representing the extent to which thefocusing lens 203 needs to be driven to achieve a focus match, basedupon the defocus quantity having been calculated. The body controldevice 101 then executes lens drive control before the operation returnsto step S310. The body control device 101 executing the lens drivecontrol transmits a drive instruction to the lens control device 201 sothat the focusing lens 203 is driven by an extent corresponding to thelens drive quantity having been calculated in step S370. In response tothis drive instruction, the lens control device 203 engages the lensdrive device 206 in operation to drive the focusing lens 203.

In step S350, the body control device 101 executes the false focus matchdecision-making processing to be described later. In step S360, adecision is made as to whether or not a false focus match has beendetected. If it is decided that a false focus match has not beendetected, the current condition is a true focus match state and,accordingly, the processing shown in FIG. 11 ends. If, on the otherhand, it is decided that a false focus match has been detected, theoperation proceeds to step S390, in which the body control device 101determines the direction along which the focusing lens 203 needs to bedriven in order to lengthen the cycles of the cyclical pattern formed onthe light receiving element array 12.

For instance, if following the start of the processing shown in FIG. 11,the operation has proceeded to step S390 after deciding, in step S340,that the current condition is not a focus match state, and accordingly,driving the focusing lens 203 so as to achieve a focus match state, “thedrive direction along which the cycles of the cyclical pattern arelengthened” is the direction opposite from the direction in which thefocusing lens 203 has been driven.

It is to be noted that if, following the start of the processing in FIG.11, the operation has proceeded to step S390 without driving thefocusing lens 203 even once, the focusing lens 203 should first bedriven along a specific direction and then the cycles in the cyclicalpattern should be checked to determine if the cycles have beenlengthened. At this time, if the cycles have been shortened, thefocusing lens 203 should be driven along the direction opposite from thedirection in which the focusing lens 203 was initially driven and thus,it is possible that the focusing lens 203 should be driven along the“drive direction along which the cycles of the cyclical pattern arelengthened”.

In step S395, the body control device 101 executes drive control for thefocusing lens 203 so as to drive the focusing lens 203 by a specificextent along the particular direction having been determined in stepS390. In more specific terms, it transmits a drive instruction to thelens control device 201 so as to drive the focusing lens 203 by aspecific extent along the direction. Subsequently, the operation returnsto step S310 to repeatedly execute the processing starting with thecharge control for the light receiving element array 12.

FIG. 12 presents a flowchart of the false focus match detectionprocessing called up in step S350 in FIG. 11. As is the processing shownin FIG. 11, this processing is included in the control program executedby the body control device 101. First, in step S400, the body controldevice 101 detects the light receiving element achieving the greatestlight reception output (i.e., the peak position in the light receptionoutputs) among the various light receiving elements having been used inthe phase difference detection in step S330 in FIG. 11. In the followingstep S405, the body control device 101 extracts a characteristicquantity pertaining to the image having been projected via thecorresponding micro-lens 13 from the light reception outputs from thelight receiving element group 14 (the light receiving element group 14covered by the micro-lens 13 that covers the light receiving element) towhich the light receiving element, having been detected in step S400belongs. The characteristic quantity is determined in correspondence toa color, a shape, a height, a position, a width, an area and the likepertaining to the image, and no restrictions whatsoever are imposed withregard to the characteristic quantity as long as it enables recognitionof at least a cyclical pattern such as that shown in FIG. 10( b). In thefollowing step S410, the body control device 101 recognizes the cyclicalpattern based upon the extracted characteristic quantity.

In step S420, the body control device 101 makes a decision as to whetheror not a cyclical pattern has been recognized. Upon deciding that acyclical pattern has been recognized, the operation proceeds to stepS410 to decide that the current condition is a false focus match state.In other words, it is decided that the defocus quantity, having beencalculated in step S330 in FIG. 11, is not correct.

The camera system in the second embodiment described above achieves thefollowing advantages.

(1) Based upon the light reception outputs from light receiving elementgroups 14, each disposed on the rear side of one of a plurality ofmicro-lenses 13 disposed in a two-dimensional array and each made upwith a plurality of light receiving elements, the body control device101 recognizes the pattern of a subject image fowled via the pluralityof micro-lenses 13 onto the light-receiving surface of the lightreceiving element array 12, and executes focus adjustment optimal forthe recognized pattern by detecting the phase difference between a pairof light fluxes having passed through different areas of thephotographic optical system based upon light reception outputs providedfrom the light receiving element array 12. As a result, accurate andefficient focus adjustment optimal for the subject pattern is enabled.

(2) After recognizing a cyclical pattern, the body control device 101determines that the current condition is a false focus match state, evenif a focus match state is detected, and re-executes the focus detectionoperation by narrowing the angle of detection range. Through thesemeasures, accurate and efficient focus adjustment is enabled even whenthe subject has, for instance, a striped pattern, which tends to readilycause a false focus match.

(3) Upon recognizing an edge pattern, the body control device 101selects fewer than usual light receiving element groups 14 from lightreceiving element groups 14 set in a single row running perpendicular tothe detected edge, and generates a pair of signal strings to be used forpurposes of image shift detection operation, by sampling outputs fromthe selected light receiving element groups 14. Through these measures,accurate and efficient focus adjustment is achieved for a subject with aclearly defined edge by excluding any influence of noise and the likepresent in areas other than the edge area. In addition, since signalstrings that are shorter than normal are used, the focus detectionoperation can be executed at higher speed.

(4) Upon recognizing a gradation pattern, the body control device 101generates a pair of signal strings and then immediately executes animage shift detection operation without applying a high pass filter tothe signal strings. In addition, if the difference between the highsignal level and the low signal level in the pair of signal stringshaving been generated is less than a predetermined value, it decidesthat the subject 31 is a low contrast subject requiring improvedaccuracy in the image shift detection operation and accordingly,generates a pair of signal strings by sampling outputs from a greaternumber of light receiving elements. Through these measures, accurate andefficient focus adjustment is achieved for a subject such as a gradationsubject for which focus detection cannot be easily executed.

The following variations are also within the scope of the presentinvention, and any one of or a plurality of the variations may beadapted in combination with either of the embodiments.

(Variation 1)

While five light receiving element groups 14 a through 14 c, taking upconsecutive positions along the lateral direction, are selected forpurposes of focus detection in the example described in reference toFIG. 3, focus detection may be executed by using light receiving elementgroups 14 set side-by-side in a single row running along a differentdirection. In addition, more or fewer than five light receiving elementgroups 14 may be selected and it is not strictly necessary to selectconsecutive light receiving element groups 14. For instance, lightreceiving element groups 14 disposed at every second position may beselected.

(Variation 2)

Instead of re-executing the focus detection operation by narrowing theangle of detection range upon deciding that the current condition is afalse focus match state after recognizing a cyclical pattern, thedirection in which the focusing lens 203 is driven may be reversed. Forinstance, if it is decided that the current condition is a false focusmatch state after or while the focusing lens 203 is driven toward theclose-up position, focus detection may be re-executed by driving thefocusing lens 203 toward the infinity position.

(Variation 3)

The patterns recognized by the body control device 101 in theembodiments described above, i.e., a cyclical pattern, an edge patternand a gradation pattern, are examples and the body control device 101may recognize another pattern and execute focus detection operation andfocus adjustment control optimal for the particular pattern. Inaddition, the body control device 101 may recognize a cyclical patternonly or an edge pattern only.

(Variation 4)

The present invention may be adopted in conjunction with a micro-lensarray 11 and a light receiving element array 12 different from thoseshown in FIG. 2. For instance, the micro-lenses 13 and the lightreceiving element groups 14 may be arrayed with array patterns differentfrom those shown in FIG. 2. They may, for instance, be disposed in asquare array pattern. In addition, the micro-lenses 13 may assume theshape other than the circular shape (e.g., a hexagonal shape). The lightreceiving elements constituting the light receiving element groups 14may be disposed in a pattern other than the square array pattern. Forinstance, light receiving elements may be disposed so that the lightreceiving element groups 14 assume a shape better approximating thecircular shape of the micro-lenses 13, or light receiving elements maybe disposed in in a single lateral row or in a single longitudinalcolumn. Furthermore, the light-blocking mask present between themicro-lenses 13 may be omitted.

(Variation 5)

Light receiving elements other than the three light receiving elementsat the left end and the three light receiving elements at the right endof each light receiving element group shown in FIG. 4( a) may beselected and used when generating a pair of signal strings for purposesof focus detection. In addition, it is not strictly necessary that sumsof pixel values be calculated. Namely, while the values a(1), a(2) andthe like are each calculated by adding up the light reception outputsfrom three light receiving elements in the example presented in FIG. 4(a), the light reception output from a single light receiving element mayinstead be designated as a(1), a(2) or the like.

(Variation 6)

The current condition may be determined to be a false focus match stateif it is decided, through focus detection executed after recognizing apattern other than a cyclical pattern, that a focus match has beenachieved. It is because a uniform image is bound to be formed on therear side of a single micro-lens 13, as illustrated in FIG. 5( c) in atrue focus much state.

(Variation 7)

A cyclical pattern may be recognized through a method other than thepattern matching method described earlier. For instance, a cyclicalpattern may be recognized by detecting, via a single light receivingelement group 14 covered by a given micro-lens 13, edges that run alonga specific direction (e.g., the lateral direction, the longitudinaldirection or a diagonal direction) in the light reception outputs fromthe light receiving element group. The term “edge” in this contextrefers to a point at which the light reception outputs of two adjacentlight receiving elements indicate a significant change (exceeding apredetermined threshold value). In this situation, the intervals betweenthe edges that are detected represent the pattern cycles.

In addition, a cyclical pattern may be recognized by calculating thesums of outputs, each in correspondence to one of a plurality of lightreceiving element groups 14, which, in turn, are each covered by one ofa plurality of micro-lenses 13 disposed along a specific direction, andcomparing the plurality of sums thus calculated. When the photographicoptical system is in a focus match state, the rear surface of a givenmicro-lens 13 is uniformly irradiated with light as shown in FIG. 5( c).This means that if the subject image assumes a cyclical pattern, thedifference between the sums of the outputs from two light receivingelement groups 14 set next to each other is bound to be large, as shownin FIG. 10( c). Namely, an edge can be detected based upon the sums ofthe outputs from two adjacent light receiving element groups 14. In afalse focus much state, in contrast, a cyclical pattern is formed on therear surface of each micro-lens 13 and in such a case, the differencebetween the sums of the outputs from two adjacent light receivingelement groups 14 is bound to be relatively small. Thus, by adding upthe light reception outputs from each light receiving element group 14and detecting edges through comparison of the sums of the outputs eachcorresponding to a light receiving element group 14, a cyclical patterncan be recognized.

(Variation 8)

The present invention may be adopted in a camera, widely known as asingle lens reflex camera, that includes a quick return mirror. Thequick return mirror in the single lens reflex camera adopting thepresent invention should be configured by disposing a sub mirror at therear surface of a quick return mirror so as to ensure that part of thesubject light having entered the quick return mirror is transmittedthrough the quick return mirror and enters the sub mirror, and that thesubject light reflected at the sub mirror enters the focus detectionunit 104. In addition, the present invention may be adopted inconjunction with an image sensor 102 configured with a micro-lens array11 and a light receiving element array 12, as is the focus detectionunit 104, and in such a case, focus detection and still image capturingmay both be executed via the light receiving element array 12 in theimage sensor 102.

(Variation 9)

The lens drive device 206 and the aperture drive device 207 may bedisposed at the camera body 100 instead of at the interchangeable lens200. In such a configuration, the actuators (not shown) in the lensdrive device 206 and aperture drive device 207 will adopt structuresthat allow the drive forces imparted thereby to be respectivelytransmitted to the focusing lens 203 and the aperture 205 in theinterchangeable lens 200 via drive mechanisms (not shown).

As long as the features characterizing the present invention are notcompromised, the present invention is in no way limited to theparticulars of the embodiments described above, and other modes that areconceivable within the technical scope of the present invention are alsowithin the scope of the invention.

The disclosures of the following priority applications are hereinincorporated by reference:

-   Japanese Patent Application No. 2012-100150 filed Apr. 25, 2012-   Japanese Patent Application No. 2012-158796 filed Jul. 17, 2012

EXPLANATION OF REFERENCE NUMERALS

1 . . . camera, 100 . . . camera body, 101 . . . body control device,102 . . . image sensor, 103 . . . half mirror, 104 . . . focus detectionunit, 106 . . . eyepiece lens, 108 . . . electronic viewfinder unit, 110. . . monitor, 200 . . . interchangeable lens, 201 . . . lens controldevice, 202, 204 . . . lens, 203 . . . focusing lens, 205 . . .aperture, 206 . . . lens drive device, 207 . . . aperture drive device

1. A focus detection device, comprising: a plurality of micro-lenses atwhich light fluxes having been transmitted through an image formingoptical system enter, disposed in a two-dimensional array pattern; aplurality of light receiving elements disposed in correspondence to eachof the plurality of micro-lenses; a focus detection unit that executes adetection of a defocus quantity of the image forming optical system bydetecting, based upon outputs from the plurality of light receivingelements, a phase difference manifested by a plurality of light fluxeshaving passed through different areas of the image forming opticalsystem; and a recognition unit that recognizes, based upon the outputsfrom the plurality of light receiving elements, characteristics of asubject image formed onto the plurality of light receiving elements viathe plurality of micro-lenses, wherein: the focus detection unit detectsthe defocus quantity through a method optimal for the characteristics ofthe subject image recognized by the recognition unit.
 2. A focusdetection device according to claim 1, wherein: the characteristics ofthe subject image manifest as a pattern in the subject image.
 3. A focusadjustment device, comprising: a plurality of micro-lenses disposed in atwo-dimensional array pattern so as to allow light fluxes, having beentransmitted through an image forming optical system, to enter thereat; aplurality of light receiving elements disposed in correspondence to eachof the plurality of micro-lenses on a rear side of the micro-lens; arecognition unit that recognizes, based upon light reception outputsfrom the plurality of light receiving elements, a pattern in a subjectimage formed onto the plurality of light receiving elements via theplurality of micro-lenses; and a focus adjustment unit that executesfocus adjustment for the image forming optical system by detecting,based upon the light reception outputs, a phase difference manifested bya pair of light fluxes having passed through different areas of theimage forming optical system, wherein: the focus adjustment unitexecutes focus adjustment optimal for the pattern in the subject imagerecognized by the recognition unit.
 4. A focus adjustment deviceaccording to claim 3, wherein: the recognition unit is capable ofrecognizing at least a cyclical pattern, an edge pattern and a gradationpattern.
 5. A focus adjustment device according to claim 3, wherein: incorrespondence to the pattern in the subject image recognized by therecognition unit, the focus adjustment unit switches at least one of;positions of a plurality of light receiving elements selected forpurposes of generating a pair of signal strings for phase differencedetection, a width represented by the pair of signal strings, a quantityof light receiving elements to be used when generating the pair ofsignal strings and whether or not to remove a low-frequency signal fromthe pair of signal strings.
 6. A focus adjustment device according toclaim 3, wherein: the focus adjustment unit makes a decision, based uponthe pattern in the subject image recognized by the recognition unit, asto whether or not the detected phase difference indicates a false focusmatch.
 7. A focus adjustment device according to claim 6, wherein: upondeciding that the detected phase difference indicates the false focusmatch, the focus adjustment unit again detects the phase differencebased upon the pair of light fluxes forming a smaller opening angle. 8.A focus adjustment device according to claim 6, wherein: upon decidingthat the detected phase difference indicates the false focus match, thefocus adjustment unit reverses a direction along which a focusing lensincluded in the image forming optical system is driven.
 9. A focusadjustment device according to claim 6, wherein: if the recognition unitrecognizes a nonuniform pattern formed, via each of the plurality ofmicro-lenses, on the plurality of light receiving elements disposed onthe rear side of the micro-lens, and the detected phase difference isequal to or less than a predetermined threshold value, the focusadjustment unit decides that the detected phase difference indicates thefalse focus match.
 10. A focus adjustment device, comprising: aplurality of micro-lenses disposed in a two-dimensional array pattern soas to allow light fluxes, having been transmitted through an imageforming optical system that includes a focusing lens, to enter thereat;a plurality of light receiving elements disposed in correspondence toeach of the plurality of micro-lenses at positions at which the lightfluxes, having been transmitted through the micro-lens, enter; arecognition unit that recognizes, based upon light reception outputsfrom the plurality of light receiving elements, a cyclical pattern in asubject image formed via the plurality of micro-lenses on the pluralityof light receiving elements; a phase difference detection unit thatdetects, based upon the light reception outputs, a phase differencemanifested by a pair of light fluxes having passed through differentareas of the image forming optical system; and the focus adjustment unitthat executes focus adjustment for the image forming optical system bydriving the focusing lens based upon the phase difference detected bythe phase difference detection unit, wherein: if the cyclical pattern isrecognized by the recognition unit, the focus adjustment unit drives thefocusing lens along a direction in which cycles in the cyclical patternare lengthened.
 11. A focus adjustment device according to claim 10,wherein: the recognition unit executes a Fourier transform on the lightreception outputs and recognizes the cyclical pattern in a spatialfrequency range.
 12. A focus adjustment device according to claim 10,wherein: the recognition unit recognizes the cyclical pattern bydetecting edges from light reception outputs from the plurality of lightreceiving elements corresponding to at least one micro-lens among theplurality of micro-lenses.
 13. A focus detection device according toclaim 10, wherein: the recognition unit recognizes the cyclical patternby calculating sums of light reception outputs from the plurality oflight receiving elements corresponding to at least two micro-lensesamong the plurality of micro-lenses and comparing the two sums.
 14. Acamera equipped with a focus adjustment device according to claim 3.